Torque responsive apparatus



Aug. 7, 1951 H. scHAEvn'z 2,563,425

TORQUE RESPONSIVE APPARATUS Filed Aug. l1, 1945 3 Sheets-Sheet 1 fam/24 Mimi /'/6 In f6 ./.Q lll ll 52PM/0 ,ya

mvg/vwl Arrofwsy Aug' 7, 1951 H. scHAEvl-rz 2,563,425

TORQUE RESPONSIVE APPARATUS Filed Aug. 11, 1945 5 Sheets-Sheet 2 TTOR/Vfy Aug 7 1951 H. scHAEvlHTz 2,563,425

TORQUE RESPONSIVE APPARATUS Filed Aug. 11, 1945 3 sheets-sheet s SMU? ` JNVENTOR. //f/m/A/v Jana-w72 Patented Aug. 7, 1951 TORQUE RESPONSIVE APPARATUS Herman Schaevitz, Collingswood, N. J., assignor to Baldwin-Lima-Hamilton Corporation, a. corporation of Pennsylvania Application August 11, 1945, Serial No. 610,309

v (c1. vs -136) i s claims. 1

This invention relates to electrical dynamometers of the type used for measuring forces, particularly torsional forces, whether they be of a constant or of transient magnitude and has for an object the provision of a simple and entirely reliable dynamometer system.

Theretofore, the measurement of torque has represented a problem for which many solutions have been offered. Prior to the present invention there existed a need for a system by means of which the force applied to a rotating shaft could be directly and accurately measured, particularly where the forces are of relatively small magnitude.

In carrying out the present invention the force or torque is applied to a shaft through the medium of tension members which, because of their elasticity, dimensionally change by amounts related to the torque or to the magnitude of the applied force. Impedance changes are produced in electrical strain gages connected to the tension members. These are related to the strains produced in the tension members. The impedance changes are translated into indications of the instantaneous magnitude of the applied force. In the preferred form of my invention the electrical strain gages are shown as of the bonded wire resistance type although other forms might be used.

For a more complete understanding of the invention and for further objects and advantages thereof reference is to be had to the following description taken in connection with the accompanying drawings in which:

Fig. l is an end view of a dynamometer `embodying the invention;

Fig. 2 is a plan View of Fig. 1;

Fig. 3 illustrates diagrammatically a simplified wiring diagram which may be used in connection with the several modifications of the invention;

Fig. 4 is an exploded perspective vievv ofthe essential parts of a modified form o1 the invention;

Fig. 5 is a sectional view-of the parts of Fig. 4 in their assembled positions;

Fig. 6 is a view, partly in section, taken on the line 5 6 of Fig. 5; and

Fig. 7 is a fractional sectional view taken on the line 1 -'I of Fig. 6. v

Referring to the drawings, a dynamometer I0 has been illustrated in Figs. l and 2 as applied to a shaft II. The dynamometer itself comprises a hub member I2 having arms I3 and I4 extending outwardly therefrom along a diametral line thereof. The hub I2 is secured to the shaft Il by any suitable means such, for example, as by a key I5. The shaft I I may be either the driving end of the arm I4. The respective bosses I'I-Zll have angular outer faces which, as shown in Fig. 2, slope toward the face -of the pulley I6 to provide clearance for tension members 22 and 23. The member 22 has one end secured in a recess in a lug 24 extending from the boss IB, as by soldering. rlhe opposite end of the member 22 is similarly secured in a' recess in a lug 25 extending from the other boss I'I. Each of tension members 22 and 23 is initially secured in place with a predetermined pre-stress or tension produced therein. Thus, as shown in Fig. 2, the tension member 22 is tightly stretched across the outer shoulders I'Ia and I8a of the bosses I'I and I8. The extension or arm I3 from the hub I2 is secured to the mid portion of the tension member 22 by means of a clamping member 25 held in place by screws 21 or solder, or both. Similarly, the tension member 23 is soldered to lugs 3U and 3| extending from the bosses I9 and 20 and a clamping member 32 by means of screws 33, or solder, or both, connects the extension or arm I4 to the mid portion thereof. The lugs 24 and 25 have bolts 35 and 35 extending therethrough and through the body of the pulley I6. By loosening lock nuts 31 and 38 and by tightening the nuts 39 and 40 additional tension may be produced in the tension member 22. The bolts 4| and 42 extending through the lugs 30 and 3| may be similarly utilized to control the amount of tension in the strip 23. In general, it is preferred to complete the assembly of the tension members 22 and 23 at the factory with a predetermined tension existing therein, thus avoiding the need in the field to rely upon the bolts 35-36 and dll-42 to change their calibrated values.

Torque applied either to the shaft I I or to the pulley I6 will be transmitted through the tension members 22 and 23. These members are preferably formed of a material which is relatively elastic. They may be of beryllium, copper, Phosphor bronze, or a soft or relatively hard steel, depending upon the magnitude of the forces to be measured.

Referring particularly to Fig. 1, it will be assumed that torque is applied to the shaft II to rotate'it in a clockwise direction and that the pulley i6 is restrained by the absorption of power through any well understood means, such as a brake or electrical generator or in driving or moving a load or in transmitting a force to a machine or some part thereof. The arm or projection I3 will increase the stresser tension in the left hand part of the tension member 22? while it Will decrease the stress or tension in the right hand section of member 22. At the same time,V the arm or extension i4 will increaser the Ystress or tension in the right hand section of themcmber 23 while decreasing the stress .or tension inthe. left hand section thereof. To secu-re rnaximunr response from the redistribution of the stresses,

strain gages 5 58 are bonded. .to the .respective right and left hand sections of the members Z2 and 23. As shown in Fig. 3, the gages i5 and: 46 form two arms of a Wheatstone bridge W while thegagesf 46 and 41 form the .remaining arms of. the. bridge. Power issupplied. to. the bridge from any Vsuitable' source as indicated by the supply terminals Y49 and: 50. Though .direct current may bef-utilized, it `is preferred that the power be sup.- plied. from Van alternating current source such as an. oscillator. The output terminals of the bridge W are' connected to an amplifier 5L. the output of which is applied .toan indica-tor and/or afrecorder 52.

The strainr gages'. 4.5--48-'are preferably of the type disclosed: in Simmons Patent 2,292,549.. lila'chV gage .consists of a lrelatively ,ne wireI or filament bonded to .thezmembers .22. and 2 3.. Each gage has the characteristic of. changing its-elec-r trical resistance .in accordance with the strain or surface .movement'of :the-members V212. and 423.. Accordingly,r the -Wheatstone bridge W will A.pret-f .erablybe in a balanced condition in the absence ofthe applica-tiener torque between theshaioll and the pulley I6. Upon application .of torque, the bridgeV Wv will be unbalanced by an amount 4related to the magnitude of. the :applied torque. The output from the bridge W either before or after amplification, .may be utilized. to actuate an indicator or' the vindicator may be combined with :a recorder, or 'the recorder alone may-be utilized tio yield a record of the magnitude of the Vapplied torque.

In practice, the dynamometer I0 vhas proved entirely ysatisfactory `in Ythe measurement of. force or of torque applied between `the-shaft andthe 'pulley I6. Its sensitivity 'is v.high and it hasibeen round reliable 1in operation. Nevertheless, if sudden overloads are-applied to thedynamometer litis possible that one: or both. of 'tensionzniembers J22 and 23 might tail. If that 'should occur, a driving connection is maintained between the driving and driven-members. Normal-ly', thearrns -or extensions I3 and Mare-*positioned niidwaylof the in-ner ends of the bosses |'|--20. Accordingly, upon failure or breakage of one or both of members- 22 and 23, the' 'extensions or arms I3 and I4 moveV into engagement with the bosses to complete a driving connection 'between the hub I2 and the pulley I6.

The modification illustrated in Figs. 4-17' combi'nes several novel features though the operation isfundamentally the same as that of Figs. 1 and '2. Thus, the tension members 22 4and 23 lrespectively carrying strain gages 45-46 and 41-48 form apart of sub-assemblies 54 and 55v respec- V'tively mounted on frame members 56 and 51.

Since these are identical in construction, onlythe -sub-assembly 55 vwill be described in detail. It

comprises the frame or 'base member -51 having f driving lug outwardly extending ledges 58 and 59 to which the tension or stress member 22 is secured, as by soldering or brazing. To the center of the stress member 22 there is attached, as by soldering or brazing, a driving lug 60. The assembly as a whole is bolted as by the bolts 6| and 62 to a flange .63 of the hub 64; To simplify the Wiring, each sub-assembly also carries a'term'inal block. As shown, the terminal block for the assembly 54 consists of members 65 of insulating material whichcarry `three terminals 66. The strain gages '45 and 46 are connected to these terminal strips as indicated. Y

l Withfbothof thesub-assemblies 54 and 55 selmined'-tothe-l1ub64, the dynamometer is completedbycarefully nesting the hub within a frame v68 of the driving pulley. It will be observed that Trame is provided with recesses 69 and 10 of shape complementary to the driving lugs 60 and TH oftheassemblies 54 and 555. Though theselugs may closely nt within the recesses 69: and 1.0 and thus not require separate fastening means, it preferred to securefthemin position byk means of` threaded? screws '|2 and 13, Figsllfand 51, extending through openings respectively located mid way of the'- recesses 69v and 10. For-example, the

screw' 13 may be moved througfhthe `opening T5 thr'eadedly to engage the `threaded''opening' inthe'. After the hub 64land frame 68 have been assembled together, a separate lrim member 76 is 'moved into place, as shown in Fig. 5..Y key Ainserted in a keyvvay '11 issprovided in'. the frame member 68 to insure a. good driving connection between and the rim 1:6..

There is then secured to one end off-the hub 61%4 a.y subsassernbly A60 comprising four slip rings Ble- 64- respectively embedded in. anV insulating member 85. This member-is secured to the'hub 64 as by fastening` screws 81'. As best shownrin Fins. LlandY 6: the hub 64 hasattened sections 68 y and' 89V which extend from the iiange 63' out-y may extend downwardly through the space 92. Y

The strain gages are preferably connected as shown in the measuring system of Fig. 3. YAccordi'nglv, stationary brushes, not shown, cooperate with the slip rings 83 and 84 to -supply power to the network including the strain gages 45--48' while the output from the network is derived from brushes, not shown, which engage the slip rings 8| and 82.

lDuring operation, `if one ofthe tension members 22 or v23 should break, driving engagement will be transferred 'from them :to four screws 94-91 respectively encircled 'by' collars, one .of which, A'the collar |00, -is shown .in Fig. 7. It'will be observed that the flange 63 of. the hub 6.4 is provided with countersunk openings through which extend the screws 94-91. .Each opening is .of substantially greater .diameter than the collar |00. Thus, as shown in Fig. "l, it will `be seen that the opening 99 provides clearance hetween its wall and the outer surface of the collar |00.V The height of the collarV |00 is sufficiently great to hold va washer 98 above `the shoulder of the countersunk opening 99. Accordingly, upon breakage of one of themembers 22 or 23 the driving connection will be transferred to the collars which are thereupon moved against the sides of the respective openings in which they are disposed.

While preferred modications of the invention have been described, it will be understood other modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A dynamometer comprising a member movable about an axis and having at least two arms extending diametrically thereof, a second member associated therewith, a pair of prestressed elements extending on opposite sides of said arms and carried by said second member adjacent the ends of said arms, means securing the respective ends of said arms to said prestressed elements for transmission of forces from one to the other of said members, and a pair of wire type strain gages whose wire is bonded throughout its effective length to the surface of each of said prestressed elements on opposite sides of said arms so as to be directly responsive to strain of the material of which said elements are formed.

2. A torque pulley comprising a hub member, a separate body member, means including a pair of prestressed elements secured to and disposed on opposite sides of the center of one of said members, means connected to the other of said members and secured to the respective mid portions of each of said prestressed elemen's and forming therewith a driving connection between said members, and wire type strain gages whose wire is bonded throughout its effective length to the surface of each prestressed element on opposite sides of said mid portions thereof so as to be directly responsive to strain of the material of which said elements are formed.

3. A torque pulley comprising a body member and a hub having an outwardly extending flange with recesses provided in diametrically opposite sides thereof, means including prestressed elements supported from said hub and extending across each of said recesses, a lug connected to the mid portion of each prestressed element to form a unit therewith, said body member having means disposed in driving engagement with said lugs, and strain gages bonded to each of said prestressed elements.

4. A sub-assembly for a torsion dynamometer comprising a frame member having projections spaced one from the other and each of the same being disposed on the same side of the torsional axis and radially spaced relative thereto to provide a predetermined moment arm, an elastic element having a lengthwise surface extending in a straight line between said projections so vas, to be tangent to a circle concentric to the torsional axis and of a radius equal to said moment arm, means for firmly securing said elements to said projections and subjecting the elements to a. predetermined initial stre-ss which causes said element to be taut, means for applying a force intermediate the ends of said element and length- `wise thereof, and a strain gage bonded to said element on either side of said force applying means.

5. A replaceable sub-assembly for a torsion dynamometer comprising a frame member having a pair of projections spaced one from the other and each of the same being disposed on the same side of the torsional axis and radially spaced relative thereto to provide a. predetermined 4moment arm, an elastic element having a lengthwise surface extending in a straight line between said projections so as to be tangent to a circle concentric to the torsional axis and of a radius equal to said moment arm, means for rmly securing said elements to said projections and subjecting the elements to a predetermined stress, a terminal block: carried by said frame member, force applying means carried by said element intermediate the ends thereof, strain gages bonded to said element cn opposite sides of said force applying means, and lead wires connecting said strain gages to said terminal block.

6. A torsion dynamometer comprising a driving member and a driven member respectively having axes about which they move angularly, a pair of tension load transmitting elastic elements each extending along straight lines respectively disposed on diametrically opposite sides of the axis of one of said members and being carried thereby, means associated with the other of said members for completing a driving connection to the respective elements intermediate the ends thereof, means whereby said elements are adapted to be initially prestressed, means operable upon failure of one of said elements for completing a rigid driving connection between said members, and means for determining the load transmitted through said elastic elements.

HERMAN SCHAEVITZ.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 195,837 Nagle Oct. 2, 1877 2,007,505 Smith July 9, 1935 2,053,560 Janovsky Sept. 8, 1936 2,252,464 Kearns et al. Aug. 12, 1941 2,260,036 Kuehni Oct,l 21, 1941 2,350,072 Simmons May 30, 1944 2,377,212 Cottrell May 29, 1945 2,403,952 Ruge July 16, 1946 FOREIGN PATENTS Number Country Date 25,382 France Oct. 24, 1922 

